Discussion:
Can you guess 21.2 CC two-stroke RPM?
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John Doe
2012-10-15 04:42:50 UTC
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I'm hoping somebody in here can guess what the RPM of a two-stroke
21.2 CC grass trimmer might be?

Out of curiosity... What's the displacement and RPM of a typical
gasoline engine RC aircraft?

FWIW. This is the grass trimmer owners manual, PDF document.

http://www.homedepot.com/catalog/pdfImages/d5/d568fa43-a88c-4a23-9bbd-8d0077b1ee26.pdf
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Thanks.
High Plains Thumper
2012-10-15 16:42:28 UTC
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Post by John Doe
I'm hoping somebody in here can guess what the RPM of a two-stroke
21.2 CC grass trimmer might be? Out of curiosity... What's the
displacement and RPM of a typical gasoline engine RC aircraft? FWIW.
This is the grass trimmer owners manual, PDF document.
http://www.homedepot.com/catalog/pdfImages/d5/d568fa43-a88c-4a23-9bbd-8d0077b1ee26.pdf
Your best bet is to subscribe to RCGroups.com, and ask these questions
there.
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HPT
George Hostler
Charlie+
2012-10-17 08:10:36 UTC
Permalink
On Mon, 15 Oct 2012 04:42:50 +0000 (UTC), John Doe
Post by John Doe
I'm hoping somebody in here can guess what the RPM of a two-stroke
21.2 CC grass trimmer might be?
Out of curiosity... What's the displacement and RPM of a typical
gasoline engine RC aircraft?
FWIW. This is the grass trimmer owners manual, PDF document.
http://www.homedepot.com/catalog/pdfImages/d5/d568fa43-a88c-4a23-9bbd-8d0077b1ee26.pdf
I have had a 17cc B&D strimmer for years could easily take a tacho
reading if that would help? NB speeds up quite a bit when the cutting
nylons get worn down short so ther is a bracket of RPM.
C+
John Doe
2012-10-17 20:23:06 UTC
Permalink
Post by Charlie+
Post by John Doe
I'm hoping somebody in here can guess what the RPM of a
two-stroke 21.2 CC grass trimmer might be?
Out of curiosity... What's the displacement and RPM of a typical
gasoline engine RC aircraft?
FWIW. This is the grass trimmer owners manual, PDF document.
http://www.homedepot.com/catalog/pdfImages/d5/d568fa43-a88c-4a23-
9bbd-8d0077b1ee26.pdf
I have had a 17cc B&D strimmer for years could easily take a
tacho reading if that would help?
If it's two-stroke, and no trouble, Yes, thanks.
Post by Charlie+
NB speeds up quite a bit when the cutting nylons get worn down
short so ther is a bracket of RPM.
I'm concerned about maximum RPM.
Charlie+
2012-10-18 13:04:12 UTC
Permalink
On Wed, 17 Oct 2012 20:23:06 +0000 (UTC), John Doe
Post by John Doe
Post by Charlie+
Post by John Doe
I'm hoping somebody in here can guess what the RPM of a
two-stroke 21.2 CC grass trimmer might be?
Out of curiosity... What's the displacement and RPM of a typical
gasoline engine RC aircraft?
FWIW. This is the grass trimmer owners manual, PDF document.
http://www.homedepot.com/catalog/pdfImages/d5/d568fa43-a88c-4a23-
9bbd-8d0077b1ee26.pdf
I have had a 17cc B&D strimmer for years could easily take a
tacho reading if that would help?
If it's two-stroke, and no trouble, Yes, thanks.
Post by Charlie+
NB speeds up quite a bit when the cutting nylons get worn down
short so ther is a bracket of RPM.
I'm concerned about maximum RPM.
Ok Here you go...
Max rpm with full length nylons = 6701
Max rpm with worn down nylons to 2" = 7524
At the 7524 figure the engine is beginning to miss slightly so for full
power strokes use the 6701 figure. There is no gearing so this is the
engine rpm. Accuracy +1/-1 rpm. The engine is properly tuned.
C+

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